2026 ICD-10-CM Diagnosis Code K31.6Fistula of stomach and duodenum
ICD-10-CM Codes›K00–K95›K20-K31›K31
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
K31.6 is a billable ICD-10-CM diagnosis code for fistula of stomach and duodenum. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 391 through 392. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 10 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified disorders of stomach and duodenum.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acquired gastric fistula
- Aortic fistula
- Aortointestinal fistula
- Duodenal fistula
- Duodenal stump fistula
- Duodenoaortic fistula
- Duodenocolic fistula
- Duodenoenteric fistula
- Duodenorenal fistula
- Enterocolic fistula
- Enterocutaneous fistula
- Enteroenteric fistula
- Esophagoenteric fistula
- External duodenal fistula
- External gastric fistula
- External gastrointestinal fistula
- External small bowel fistula
- Gastric fistula
- Gastrocolic fistula
- Gastroduodenal disorder
- Gastroduodenal fistula
- Gastrointestinal fistula
- Gastrojejunal fistula
- Gastrojejunocolic fistula
- High-output external gastrointestinal fistula
- Internal duodenal fistula
- Internal gastric fistula
- Internal gastrointestinal fistula
- Jejunal fistula
- Low-output external gastrointestinal fistula
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Gastrocolic fistula
- Gastrojejunocolic fistula
Code Also
- , if applicable, disruption of internal operation surgical wound T81.32
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
duodenum K31.6
gastric K31.6
gastrocolic K31.6
gastroenterocolic K31.6
gastroesophageal K31.6
gastrojejunal K31.6
gastrojejunocolic K31.6
stomach K31.6
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Gastric Fistula
abnormal passage communicating with the stomach.Stomach
an organ of digestion situated in the left upper quadrant of the abdomen between the termination of the esophagus and the beginning of the duodenum.
Patient EducationClinical
Fistulas
A fistula is an abnormal connection between two parts inside of the body. Fistulas may develop between different organs, such as between the esophagus and the windpipe or the bowel and the vagina. They can also develop between two blood vessels, such as between an artery and a vein or between two arteries.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert K31.6 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About K31.6Overview
What is the ICD-10 code for fistula of stomach and duodenum?
The ICD-10-CM code for fistula of stomach and duodenum is K31.6 (sometimes written as K316). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is K31.6 (Other diseases of stomach and duodenum) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report fistula of stomach and duodenum on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does K31.6 group to?
When fistula of stomach and duodenum is the principal diagnosis on an inpatient stay, it groups to MS-DRG 391, 392, with relative weights from 0.7796 to 1.2683 depending on complications. Higher weights mean higher Medicare reimbursement.
Is K31.6 a CC or MCC?
CMS lists K31.6 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 10 closely related codes in its exclusion list.
What is the ICD-9 equivalent of K31.6?
Under the General Equivalence Mappings, fistula of stomach and duodenum converts to ICD-9-CM 537.4 (gastric/duodenal fistula). The mapping is a direct match.
